Can't see them staying independent very long. They may be looking beyond Sun Belt. They only have a 19,000-seat stadium but I'm sure money's not an issue if they want to expand. They might easily move into CUSA if one its teams gets plucked in the next expansion or if it wants to add a 16th team. CUSA doesn't currently have any religious schools in its membership, but it did in the past.
TBH, if the MAC was hell bent on expansion, I wouldn't mind expanding into Virginia. But I like the current 12 team set up just fine (unless we're serious about dumping EMU for attendance woes, b/c I'd swap Liberty for Ypsi State Community College in a heartbeat).
I agree that CUSA is probably the ultimate landing spot. CUSA has that weird 13 team set up right now, but they'd have to kick an East team to the West to get a 7/7 team balance in their divisions. MTSU is probably the best candidate for that, but you'd leave WKU on an island a bit. Lynchburg is probably far enough from Norfolk that ODU wouldn't gripe too much about a second Virginia school in the leage.